That "might" be part of one of the dummy plugs.

 

looks like the forward clutch orfice restrictor that goes above the "valve body"
Its rightful place is in the rear bolt cavity (out of the two hollow bolts)
a dab of vaseline should hold it long enough to get vb back in place.
or if left out it might cause harsh engagements or shifts?

 

I just posted about the same part. Its the forward clutch orifice plate/washer. Ford has upgraded it to a orifice bolt. If it does not stay pressed up in the tube against the bolt, it will cause shift issues...